Alloy



iii

I atentod. July 18, 1939 PATENT OFFICE Arthur W. Peterson,

liner to Metals a Controls Corporation,

ALLOY North Attlcboro, Mala, al-

Attict boro, Man, a corporation of Mauaohnse to No Drawing. Application December 2, 1988,

Serial No. 243.529

Claim.

This invention relates to alloys, and with regard to certain more specific features, to gold alloys.

This application is in part a continuation of my copending application Serial Nc. 226,328, filed August 23, 1938.

Among the several objects of the invention may be noted the provision of a gold alloy which may be used to manufacture either so-called "solid gold objects or gold-plated objects, which gold alloy will wear longer than other gold alloys of similar karate and colors, when subjected to the wear normally encountered by articles of jewelry that are worn on the hands and wrists, etc, or clothing; the provision of a gold alloy which has an exceedingly fine, close grain. which fineness and closeness of grain make much easier the manufacture of articles from the alloy, and prevent what is known as "orange peel" (surface roughness caused by abnormally large crystals of metal being set in relief by mechanical wormng oi the metal such as bending and other manufacturing operations) during the manufacture of articles of Jewelry from the gold alloy: the provision of a gold alloy which may be used either as solid gold or as gold plate which has much greater resistance to tarnish and corrosion encountered in atmospherlcconditlons and in perspiration acids, etc.; and the" provision of a gold alloy which, hardness for hardness, is adapted to higher annealing and soldering, temperatures in the manufacture of jewelry article irom it than other gold alloys now available. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the ingradients and combinations of ingredients, the proportions thereof, and ieatures of composition, which will be exemplified in the products hereinaiter described, and the scope of the application of which will be indicated in the i'ollowing claims.

in the manufacture of plated gold articles of jewelry, one of the dimculties encountered is the provision of a gold plate which will stand up against the abrasion caused by clothing, etc. when the article is being Wars. The gold plate on such an article is generally very thinyand the life of a plated gold article is determined to a great extent by the resistance to abrasion of the gold plate itself. It has been possible in the past to provide gold alloys of a given karat which will withstand wear to a greater degree than alloys commonly in use. This is ordinarily done by adding to the gold alloy metals oi harder nature in considerable amounts. The eflect on the alloy is to give it greater hardness, but the resulting color, from the standpoint of the Jewelry undustry, is not as good as it was before. Consequentlyit has been somewhat o a p oblent to provide a hard gold alloy in a given karat which would present a color which, for the given karat of the gold, would be acceptable to the jewelry industry. The alloy which is the subject 0! this invention provides a metal which for a given karat and given color has much greater wear ce than other hitherto lmown gold al- In the manufacture of articles of jewelry from gold, it is customary in many cases to use a goldplated stock. In the subsequent bending, stretching, and shaping operations, etc, of the article, the gold plate has a tendency to present a rough crystalline appearance on the surface. This phenomenon is commonly called orange peel in the jewelry and allied industries. It is a serious defect and great pains must be taken to prevent it in the manufacture of jewelry items. The present invention discloses an alloy which has a very fine, close grain which to a great extent prevents this so-called orange peel. This line, close grain is inherent in the structure, and while fine, close grains can be obtained in other bold alloys, it is only at the expense of much mechanical working. The cobalt addition, which is a provision of this invention, prevents abnormal crystal size in the alloy. The present alloy thus provides a metal which atiords in either case, cold-worked or annealed condition a fine, close grain.

Among the many difficulties encountered in the provision of gold alloys for the jewelry industry, is the difflculty of tarnish and corrosion of the gold by atmospheric conditions and by the acids commonly present in the perspiration of individuals. For example, in the optical goods industry, it is no common occurrence to receive complaints from customers regarding, the tact that various parts 01' theirspectacle frameshave become eaten away on the surface by the skin acids, with resulting roughness and raggedness of the metal, which in turn causes skin irritation where it comes in contact with the skin. This is caused by the fact that the perspiration acids have eaten away the gold plate which covers a plated spectacle frame. This destruction of the gold plate is a very common occurrence in all goldplated articles of jewelry which come in contact with the skin of the wearer. One of the solutions in the past has been to substitute a gold alloy for the plate which has a richer gold content. This is a necessarily expensive procedure and one that it is desired to avoid. The gold al- 107 which is the subject of the present invention provides a metal which has greater tarnish andcorrosion resistance to skin acids, etc. than other known alloys of similar karat and color.

In the manufacture of many articles of jewelry, either the gold-plated variety or the solid karat gold variety. it is necessary many times in the course of manufacture. to submit the article to either high annealing temperatures or high soldering temperatures. The tendency of hitherto known gold alloys of similar color has been for the alloys to soften unduly with this treatment, creating distortion and too great flexibility in the finished article. For example, inthe manufacture of watch cases, which are made of very thin material (relatively speakin at one stage of the manufacture the watch cases must be anhealed, and at another point they must have the hinges soldered on. One diiiiculty that has been encountered is that the watch case itself will buckle due to stresses in the metal being relieved too unevenly. Furthermore, the finished watch case will be so soft that in its use. it is apt to twist and distort in shape, thus causing misalignment of parts and possibly damage to the contained delicate mechanism. Furthermore, many gold or gold-plated articles of desirable color for their karat, wear excessively in use. This is caused by softness in the finished article caused by necessary annealing operations during the manufacturing processes. The present gold alloy is one that provides a metal which is adapted (for given hardness) to higher annealing and soldering temperatures. For example, if the watch case mentioned above were to be annealed at, say, 800 F., it would come out with a certain softness. If the same watch case is made out of the gold alloy which is the subject of this invention, and is subjected to the same annealing temperature, the resulting case will be harder temper than in the former case. This means, of course, that the metal has more springiness and consequently more resistance to bending and buckling. It will also wear longer, an important desideratum.

The gold alloy of the present invention consists basically of gold, copper, cobalt, and zinc or cadmium.

The gold content depends upon the desired karat of the gold. The present invention relates principally to alloys within the karat range of 8 to 20; hence the proportion of gold in the alloy,

' by weight, may vary from about 33% to about to about 5%, by weight, of the 'alloy, about 1% being usually preferred. The cobalt, possibly in combinationwith the copper present, seems to act as the regulator of grain size in the alloy. If no cobalt is used, the grain size oi the alloy of the present invention is not superior to-the grain size of prior gold alloys. The zinc or cadmium content may vary from about 2% to about 12%, by weight. of the alloy,

depending partly on the desired color and partly on the desired stiffness of the alloy.

The following table gives the compositions of "several specific alloys-that have been made in area-res accordance with the teachings of the present invention.

Composition in per cent. by weight Alloy Karat Gold Copper Cobalt Cadmium Zinc A 10 41. 07 4B. 38 l. 0 None. 12.0 B 10 41. 67 46. 33 1.0 12.0 None.

The alloy designated as A above was rolled and annealed for 40 minutes at 1200 1". The reduction in rolling was 50%. The following table gives the hardness measurements (Vickers No. 5 and Rockwell B) for the resulting alloy, in thicknesses of 0.060 and 0.030 inch,.in both hard and A 5 mm. Erichsen cup made from the above 0.030 inch thick annealed alloy showed a smooth surface. with no orange peel. The grain size in the cup, determined microscopically, was about 0.005 millimeter.

The superiority of the alloys of the present invention is evident from the above.

In general, the best procedure for making up the alloys of the present invention is first to make a base alloy of the copper and'zinc or cadmium, then to modify said base alloy by adding thereto the correct amount of cobalt, and finally to alloy the cobalt-containing base alloy with fine gold.

The effect of increasing the cobalt content is to produce a paler gold (the decolorizing effect,

or paling effect, of cobalt being roughly only one fourth as great as that of nickel) and at the same time to increase its resistance to corrosion, its resistance to wear, and its temper for a given anneal or working operation. It also has a tendency to give the resulting alloy a finer, closer grain if the cobalt content is increased. The effect on the melting point of the final gold alloy of increase of cobalt is to raise the melting point.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above alloys without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

.I claim:

1. A gold alloy consisting of about 33 to 84% gold, 11 to 67% copper, 0.1 to 5% cobalt, and 2 to 12% of a metal selected from the group consisting of zinc and cadmium.

2. A gold alloy consisting of about 33 to 84% gold, 11 to 67% copper, 0.1 to.5% cobalt, and 2 to 12% zinc.

3. A gold alloy consisting of about 33 to 84% gold, 11 to 67% copper, 0.1 to 5% cobalt, and 2 to 12% cadmium.

4. A gold alloy consisting of about 41.87% gold,

45.33% copper, 1% cobalt, and 12% zinc.

5. A gold alloy consisting of about 41.67% gold, 45.33% copper, 1% cobalt, and 12% cadmium. ARTHUR W. PETERSON. 

